The EPA maintains a Toxics Release Inventory of over 650 toxic chemicals that are disposed or released from more than 20,000 industrial sites in the United States. The Department of Health and Human Services and USDA maintain a list of over 60 select agents and toxins that pose a severe risk to both human, animal and plant health. These compounds represent only a fraction of the toxins and toxicants at environmental concentrations that pose substantial risk to human health. At present, assays that assess the impact of exposure to stem cell differentiation and programming are not capable of the throughput necessary to stay apace the speed of new toxicants entering the environment. Such measurements are critical to our understanding of the risks these agents represent, and to our ability to moderate or eliminate those risks. The goal of this project is the development of instrumentation capable of detecting toxicant effects on stem cell differentiation processes in a sensitive high-content assay based on the detection of changes in the differentiation profile of stem cells exposed to these toxicants. Since stem cells are critical elements of embryonic development and for the ongoing maintenance of adult tissues, an effective assessment of their function will be important of our understanding of environmental risks for autoimmune disease, immunodeficiencies and neoplasia, to name only a few of the health risks when stem cell behavior is altered. The assay is based on instrumentation that can measure grating-coupled surface plasmon resonance (GCSPR) and grating-coupled surface plasmon coupled emissions (SPCE). This assay system will incorporate a reliable fluidic system and a simple-to-use sensor chip array that can be used for assessment of toxicant effects on stem cell differentiation and may ultimately also have value as a point-of-care diagnostic.